1. Field of the Invention
This invention generally relates to self-lubricating bearings and, more particularly, to a continuously self-lubricating and self-cleansing, non-friction compact bearing which supports a rotatable shaft such as a sleeve shaft.
2. Description of the Prior Art
Shaft-support, non-friction bearings are characterized by an inner race, an outer race, and non-friction bearing elements that rotate between the races.
There has been a long-felt need for a self-lubricating and self-cleansing, non-friction shaft support bearing system that is neither complicated to use, nor expensive to install, and that can fit within substantially the same space occupied by a conventional shaft-support bearing on existing machines.
Known oil lubrication systems are inadequate for such non-friction bearings that support horizontal shafts, and they are even worse for such bearings which support vertical shafts.
At low-to-medium shaft speeds, turbulence in the oil keeps the rotating bearings covered with a film of oil, but at higher speeds centrifugal forces tend to remove this oil film leaving damaging metal-to-metal contact.
Known is an oil mist lubricating system which utilizes a source of regulated compressed air, an oil reservoir, a mist generator, a mist-to-oil condenser, a nozzle to force the condensed oil jet into the bearing, and a pump for returning the oil from the bearing back to the oil reservoir. Obviously, such a mist system is bulky, impractical and too expensive for use with most portable machines such as concrete saws and the like. Oil when delivered to a bearing under pressure increases friction in the bearing which tends to reduce its operational life.
A mist system which does not require a source of compressed air is described in U.S. Pat. No. 2,950,943. It uses an oil reservoir situated below a slinger arm that is coupled to the rotatable shaft. The slinger splashes oil and creates a mist some of which is intended to reach the rotating bearing surfaces. This mist provides irregular and non-uniform lubrication and, even at best, does not sufficiently lubricate nor cleanse off the wear products from the bearings.
Most of the above and other well-known problems associated with self-lubricating bearings have been solved by the invention described in applicants' co-pending application Ser. No. 06/818,503 filed on Jan. 13, 1986, assigned to the same assignee. This application is incorporated herein by reference.
The present invention solves a difficult problem and differs from that described in said co-pending application primarily in that the present self-lubricating bearing requires a minimum of space and therefore is superbly suitable to replace conventional shaft-support, non-friction bearings within the cramped spaces allocated for them on existing machines. In this manner, existing machines can be retrofitted with the present self-lubricating bearings without any modifications required to be made to the machines.